Low pressure mercury vapor gas discharge lamp with amalgam

ABSTRACT

Low-pressure mercury-vapor gas-discharge lamps, particularly fluorescent ones, of high intensity and high specific power, containing an amalgam of the formulation: MERCURY15 - 20 AT. PER CENT CADMIUM53 - 38 AT. PER CENTTIN20 25 AT. PER CENT BISMUTH12 - 17 AT. PER CENT

United States Patent [1 1 Shindelman et al. I

[ June 26, 1973 LOW-PRESSURE MERCURY-VAPOR GAS-DISCHARGE LAMP WITHAMALGAM Inventors: Jury losiiovich Shindelmau, ulitsa Kalinina, 3, kv.57; Galina Iosifovna Akulova, ulitsa Tsiolkovskogo, 37, kv. 63; GalinaGrigorievna Snitka, ulitsa Birjuzova, 31, kv. 2; Nikolai lvanovichVasyagin, ulitsa Zygina, 42, kv. 54; Vladimir Vasilievich Tyabirdin,ulitsa Zygina, 42, kv. 45, all of Poltava, U.S.S.R.

Filed: Apr. 22, 1971 Appl. No.: 136,482

Foreign Application Priority Data May 25, 1970 U.S.S.R 1429909 US. Cl.313/109, 313/174 Int. Cl. Hlj 61/24 Field of Search, 313/174, 109, 179

[56] References Cited UNITED STATES PATENTS 3,007,071 /1961 Lompe et a1313/109 X 3,152,278 10/1964 Dziergwa et a1. 313/109 X PrimaryExaminer-Pa1mer C. Demeo Att0rneyHo1man & Stern [57] ABSTRACTLow-pressure mercury-vapor gas-discharge lamps, particularly fluorescentones, of high intensity and high specific power, containing an amalgamof the formulation:

mercury at, per cent cadmium 53 38 at. per cent tin 20 at. per centbismuth 12 17 at. per cent 2 Claims, 2 Drawing Figures LOW-PRESSUREMERCURY-VAPOR GAS-DISCHARGE LAMP WITH AMALGAM The present inventionrelates to electric gasdischarge lamps with an amalgam, notably ofhighintensity, 80-200 W fluorescent lamps of high specific power, andalso to fluorescent lamps of ordinary specific power, used under adversetemperature conditions, such as in unventilated enclosed lightingfixtures.

In the prior art, there are low-pressure mercuryvapor gas-dischargelamps containing various bicomponent amalgams (cadmium-mercury,indiummercury, thallium-mercury, etc.), tri-component amalgams(cadmium-tin-mercury, indium-zinc-mercury, etc.), and tetra-componentamalgams (indium cadmium-tin-mercury, lead-bismuth-cadmium-mercury).

A major disadvantage of gas-discharge lamps using the above-listedprior-art amalgams consists in that they have a high luminous yield onlyin a very narrow range of ambient temperature (40] to 55] C), while, asnumerous investigations have shown, the walls of highintensity,high-specific power fluorescent lamps used in enclosed lighting fixturesmay have a temperature of 60] to 70} C.

With fluorescent lamps of ordinary specific power, the temperature inunventilated enclosed lighting fixtures may likewise range from 45] to70] C, depending on the number of lamps enclosed.

It is an object of the present invention to avoid these disadvantagesand to provide fluorescent lamps witha luminous flux stable over a widerange of ambient temperature (from 40] to 80] C).

Another object of the invention is to provide a nontoxic solid amalgamby the proper choice of its formulation, which can be used in bothhigh-intensity, highpower and ordinary-power fluorescent lamps employedin unventilated enclosed lighting fixtures and will have a high luminousoutput over the temperature range indicated.

With these and other objects in view, the present invention resides inthat in order to ensure a stable luminous flux over a wide range ofambient temperature (from 40] to 80] C), use is made of an amalgam ofthe formulation: mercury, at. percent; cadmium, 53 38 at. percent; tin,20 at. percent; and bismuth, l2 17 at. percent.

The amalgam disclosed herein has a melting point of 190] to 210] C; itwill remain solid when used in a lamp and sufficiently plastic in thecourse of manufacture, so that it can be made into any shape (bars,balls, and the like).

The invention will be more fully understood from the followingdescription of a preferred embodiment when read in connection with theaccompanying drawings wherein:

FIG. 1 is a plot relating the luminous flux of a 80 W fluorescent lampusing a specific amalgam formulation,

to ambient temperature; FIG. 2 is a plot relating the luminous flux of a125 W fluorescent lamp using various amalgam formulations, to ambienttemperature.

Referring to FIG. 1, an amalgam of the formulation: mercury, 15 at.percent; tin, 25 at. percent; cadmium, 48 at. percent; and bismuth, 12at. percent, shifts the peak of the luminous flux into the region ofhigh temperatures. At a temperature of 80] C, the luminous flux is only8 percent below the peak.

Curves A, B, and C in FIG. 2 illustrate the performance ofa 125 Wfluorescent lamp having an envelope 150 cm long and using variousamalgam formulations. These amalgam formulations are summarized in Tablel.

TABLE I Ingredient, Curve atomic percent A B C Mercury (Hg) l5 17 20Cadmium (Cd) 48 46 38 Tin (Sn) 25 22 25 Bismuth (Bi) 12 15 17 Total 100at. percent 100 at. percent 100 at. percent This lamp has a luminouspeak in the temperature range from 65] to C. It can be operated over atemperature range of 40] to C., and its luminous flux at the limitingtemperature falls off by not more than 7 percent from the peak.

From a comparison of curves B and D (FIG. 2), it is seen that a mercurylamp (curve D) is markedly inferior to an amalgam lamp (curve B) interms of luminous flux. It has been calculated that the luminous flux ofa W fluorescent lamp using an amalgam exceeds that of a 125 Wfluorescent lamp using straight mercury by 18 percent at 50] C, by 20percent at 60] C, and by 32 percent at 70] C.

These differences are traceable to the metals used in the amalgam andtheir percentages.

The yield of mercury vapor from the amalgam is decided by intermetallicmercury-cadmium and mercurybismuth compounds. In contrast to classicalchemical bonds, ionic and covalent, these compounds feature a specificmetallic bond which invalidates the valence theory.

In the amalgams disclosed herein the formation of intermetalliccompounds depends on the percentage of mercury in the amalgam. It may bethought that the amalgam corresponding to curve B contains no freemercury.

The thermal effect on the amalgam in which the tin acts as a stabilizerof mercury yield is such that the pressure of mercury vapor is optimum(3 10.3 mm Hg) for the desired resonance radiation to be emitted in a125 W fluorescent lamp.

The high efficiency of gas-discharge lamps using an amalgam of theformulation corresponding to curve B is augmented by the fact that theydo not call for ventilated lighting fixtures of complicated design.

Since the pressure of mercury pressure over this amalgam at 201C isabout 10..5mm Hg, any contamination of the surrounding premises iscompletely eliminated.

The amalgam is prepared from inexpensive and abundant materials andcompares favorably with any of prior-art amalgams for gas-dischargelamps in terms of cost, performance and low toxicity.

What is claimed is: 1 l. A low-pressure mercury-vapor gas-dischargelamp, of high intensity and high specific power, containing an amalgamof the formulation:

mercury cadmium tin bismuth l 20 at. percent 53 38 at. percent 20 25 at.percent 12 17 at. percent.

2. A mercury vapor gas-discharge lamp as claimed in claim 1 whichincludes means rendering the lamp fluorescent.